Many geological disasters such as the debris flow and landslide caused by the rainstorm happened on 8th,9th and 10th of July in Daguangbao-Huangdongzi Gully,Sichuan Province. Based on the field investigation,the formation causes of the debris flow,developing trend and risk assessment are analyzed. The investigation results show that:① The Daguangbao-Huangdongzi Gully debris flow belongs to the typical Gully Debris flow and could be divided into Formation,Circulation and Deposit area;② The debris flow formation includes the loose material provided by Daguangbao landslide and the volume is up to 107 m3;extreme rainfall climate directly started the loose deposit to form the debris flow and the geographical conditions is conducive to the erosion,transportation and deposition of debris flow.The debris flow is still in the active stage and will be strengthened in the future;③The conclusion after the risk assessment shows that the debris flow poses a moderate risk with the fatalness degree of 0.482.%2013年7月8~10日四川省由于普降暴雨,发生多起泥石流、滑坡等地质灾害。在野外调查的基础上,对大光包-黄洞子沟特大泥石流形成原因进行分析,对未来发展趋势做出预测和危险性评价。调查结果表明：①大光包-黄洞子沟泥石流属于典型的沟谷型泥石流,可分为形成区-流通区-堆积区。②本次泥石流形成原因为体积高达1×108 m3以上的松散的大光包滑坡堆积体提供物源；极端的降雨气候直接启动松散堆积物形成泥石流；地形条件有利于泥石流侵蚀、搬运和堆积,为典型的滑坡-碎屑流-泥石流型,且仍处于活跃期,并在今后会有加强的趋势。③经过对大光包-黄洞子沟泥石流进行危险度评价可知：该泥石流危险度为0.482,属于中度危险泥石流。
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